Elon Musk’s Mars Vision: A One-Size-Fits-All Rocket. A Very Big One.

The chief executive of SpaceX, Elon Musk, at the International Astronautical Congress in Adelaide, Australia, on Friday.

ADELAIDE, Australia — Elon Musk is revising his ambitions for sending people to Mars, and he says he now has a clearer picture of how his company, SpaceX, can make money along the way.

The key is a new rocket — smaller than the one he described at a conference in Mexico last year but still bigger than anything ever launched — and a new spaceship.

Speaking on Friday at the International Astronautical Congress in Adelaide, Australia, Mr. Musk said he had figured out a workable business plan, although his presentation lacked financial figures to back up his assertions.

Mr. Musk has long talked about his dreams of colonizing Mars, and at the same conference last year, he finally provided engineering details: a humongous reusable rocket called the Interplanetary Transport System.

But he did not convincingly explain then how SpaceX, still a company of modest size and revenues, could finance such an ambitious project.

“Now we think we have a better way to do it,” he said Friday.

The new rocket and spaceship would replace everything that SpaceX is currently launching or plans to launch in the near future. “That’s really fundamental,” Mr. Musk said.

The slimmed-down rocket would be nine meters, or about 30 feet, in diameter instead of the 12-meter behemoth he described last year. It would still be more powerful than the Saturn 5 rocket that took NASA astronauts to the moon. Mr. Musk called it B.F.R. (The “B” stands for “big”; the “R” is for “rocket.”) The B.F.R. would be able to lift 150 metric tons to low-Earth orbit, Mr. Musk said.

For Mars colonists, the rocket would lift a spaceship with 40 cabins, and with two to three people per cabin, it would carry about 100 people per flight. After launching, the B.F.R. booster would return to the launching pad; the spaceship would continue to orbit, where it would refill its tanks of methane and oxygen propellant before embarking on the monthslong journey to Mars.

Elon Musk shared this image on Instagram on Friday with the caption: “Mars City. Opposite of Earth. Dawn and dusk sky are blue on Mars and day sky is red.”

But with the smaller size, the B.F.R. would also be useful much closer to Earth, Mr. Musk said. He said it would be able to take over the launching duties of SpaceX’s current Falcon 9 rocket, taking many satellites to orbit at once, as well as ferry cargo and astronauts to the International Space Station. A variation of the spaceship could be used to collect and dispose of relics of satellite and other debris cluttering low-Earth orbit, he said.

Because all parts of the rocket and the spaceship are to be fully reusable, the cost of operating them would be low.

Robert Zubrin, president of the Mars Society, a nonprofit organization that advocates human exploration and settlement of the planet, liked the changes that Mr. Musk has made. “This is a much more practical approach than he presented last year,” Dr. Zubrin said. “It means he is serious.”

The same spaceship could also land on the moon. “It’s 2017,” Mr. Musk said. “We should have a lunar base by now.”

Even on Earth, the rockets, traveling at up to 18,000 miles per hour, could make long-distance trips short — New York to Shanghai in 39 minutes, for example. Any two points on Earth would be less than an hour apart, Mr. Musk said.

After the presentation, Mr. Musk took to Instagram to elaborate on the price of those round-the-world rocket flights: “Cost per seat should be about the same as full fare economy in an aircraft. Forgot to mention that.”

Mr. Musk maintained a highly optimistic schedule for his Mars dreams. He said the company had already started work to build pieces of the new rocket.

A cargo mission, without any passengers, could launch as early as 2022. “That’s not a typo, although it is aspirational,” he said. “Five years feels like a long time to me.”

Two years later, the next time that Mars and Earth would swing by each other, SpaceX would launch four B.F.R.s to Mars — two carrying cargo, two carrying people.

In the lead-up to Mr. Musk’s talk on Friday, the main entrance to the Adelaide Convention Center was closed and locked, with a swell of people outside waiting to get in.

“He’s such an iconic character,” said Paris Michaels, the chief executive of Air@Wave Communications in Sydney, who attended the congress. “I planned the day around making this event. I’m taking a later flight home, even though I’m averaging two hours’ sleep this week.”

SpaceX is not the only company with proposals for the Red Planet. A few hours before Mr. Musk’s talk on Friday, Lockheed Martin provided an update of its own Mars mission vision, called Mars Base Camp. Compared with Mr. Musk’s ambitions, the Lockheed Martin plan seems quaint and slow. It would not head to Mars until 2028, it would take only six astronauts, and the first trip would not even land on Mars but instead circle the planet for a year before returning to Earth.

An artist’s illustration of the Mars Base Camp spacecraft proposed by Lockheed Martin.

From Mars orbit, astronauts could control robotic explorers like rovers and flying drones.

Mars Base Camp is more of a suggestion to NASA of what the agency could do rather than a corporate strategy that Lockheed Martin would pursue by itself.

“This isn’t Lockheed Martin’s vision, and it’s not the only vision of how to get to Mars, but we put it out here so that we can globally begin the dialogue,” Robert Chambers, an engineer working on the Mars Base Camp concept, said during the presentation.

Unlike Mr. Musk’s dreams, Mars Base Camp would not require unproven business plans or novel technologies far beyond what already exists or is already in development. “We know how to do this,” Mr. Chambers said.

The spacecraft, which looks as one might expect a traditional NASA expeditionary mission to Mars to look, would incorporate both the Orion crew capsule that Lockheed Martin is building for NASA deep-space missions and the agency’s plans to put a space station high above the moon. This week, the Russian space agency announced that it would like to collaborate with NASA on this lunar space station, called the Deep Space Gateway.

Lockheed Martin is one of six companies that NASA selected to develop a prototype of a habitat module that could be used for the Deep Space Gateway. Lockheed Martin officials said their vision for Mars Base Camp did not depend on their design’s being selected.

The Mars Base Camp proposal would also fit within the NASA budget, Lockheed Martin officials said.

This year’s update unveiled a reusable, hydrogen-fueled lander that would take astronauts to the Martian surface on a follow-up mission. Up to four astronauts could live on the Martian surface for two weeks at a time in the lander.

Lockheed Martin has added to its Mars Base Camp concept a lander that could take astronauts to the surface of Mars for two-week stays.

 Reflecting the interest of many to return to the moon before going to Mars, Lockheed Martin officials said the lander could also be used to travel to different parts of the moon from the Deep Space Gateway.